A careful selection of sustainable external materials and details ensure the longevity of the building’s lifespan. A low maintenance home, it has no painted external walls and low water use vegetation. It has minimal energy and water consumption having light filled spaces sheltered from the heat, north orientation with large overhangs, cross flow ventilation, high performance glazing, energy and water efficient fixtures, solar power for hot water and pool, photovoltaics and a rain water collection facility for irrigation, toilets and laundry.

The building is designed as a private home for the long term use of its owners with a high level of finish and detailing within the budget requirements.

As the rescued baroque picture goes on display following conservation work, the hunt for the artist begins

It was in the most sorry state imaginable – terribly torn, with parts peeling off, no frame, and almost black – and for about 150 years lay unloved at the back of the stores in one of the world's oldest public galleries.

Now, after a campaign that was launched in 2009 to restore it, the Dulwich Picture Gallery has put on display the baroque painting of St Cecilia, the patron saint of music – and it has turned out to be something of a stunner.

"This picture is a total dream to work on," said the gallery's chief curator, Xavier Bray. "Paintings that need a total restoration tend to be very exciting. There's always that chance you might uncover a lost Caravaggio; highly unlikely, but a chance certainly of uncovering a very good picture."

The painting looks wonderful, shines a light on the fascinating history of the gallery itself, and also raises a new mystery: just who was the painter?

The work was bought in 1790 by one of the gallery's founders, Noel Joseph Desenfans, under the impression it was by the Bolognese master Annibale Carracci. Bray said it was "not good enough" to be a Carracci, but whoever did paint it could have been inspired by the Carracci school.

Desenfans and his business partner Sir Francis Bourgeois, the gallery's other founder, thought they had a masterpiece and so wanted it hung prominently in the "skylight" room of the beautiful home they shared in what is now Hallam Street, in the West End of London.

They also wanted it hung as a companion piece to a portrait of the actor Sarah Siddons by their friend Joshua Reynolds. But that meant making it much bigger, a job that Bourgeois, a not terribly distinguished landscape painter, took on with vigour.

Exactly what was on their mind is open for debate. "I wonder whether it was about the personification of theatre on one side and in St Cecilia the personification of music," said Bray.

They may also have been paying homage to their friend Reynolds, elevating his place in art history by placing work by the still-alive English artist in the same room as Bolognese masters.

There is talk about the relationship between the two founders; some have even speculated of a ménage a trois involving Mrs Desenfans. Certainly they were close as all three are buried together in the gallery's mausoleum, their bones mixed up because of a German wartime bomb.

Whatever the truth, the Bourgeois additions were not a good thing. In 1842 the Victorian art critic Anna Jameson wrote that she had "seldom seen a picture so shamefully maltreated – so patched and repainted … [Sir Francis Bourgeois's] hand is clearly distinguishable."

Bray said: "These additions very quickly started to peel off and then eventually the canvas gets ripped and slashed and was almost totally black. It ended up in a really sad state."

In 2009 the Friends of Dulwich Picture Gallery adopted the painting and the results of the spectacular conservation can now be seen.

The gallery now very much wants to establish who the painter is.

Bray has tried all his friends in the curating world and been through all the artists of the Bolognese, Neapolitan and Veronese schools. "I've been trying all over Italy to find a similar hand. It is a really tricky one but now it's cleaned, people will be able to make a more educated guess."

Bray's best guess so far – a wild one, he cheerfully admits – is that it could be the work of a woman artist. He is aware he might be criticised for a hunch that is partly based on the artist's attention to the detail of what St Cecilia is wearing, her jewellery, and her hair. "There is a woman artist called Ginevra Cantofoli who trained in Bologna.

"I need to see much more by her and I need to go and see her work, but it does seem uncannily close.

"I'm sure it will happen one day, I'll find out who painted it. It will probably come from being in Italy, having a good lunch and stumbling in to a church and seeing an altarpiece by the same hand."

There are many other possibilities and Bray said he can sound like he's naming the Italian football team when speculating. "It's still a mystery but it's a fantastic conundrum for the gallery to have. It may even be a painting by a good painter early in his career. Could it be an early Guercino when he hasn't got it quite right?"

The painting now hangs at eye level at Dulwich, near a painting that is definitely by Carraccia, around the corner from the Reynolds and not far from a painting that Desenfans and Bourgeois also once hung in their skylight room.

Domenichino's The Adoration of the Shepherds was sold by the then cash-strapped Dulwich in the 1970s but has been loaned back to them by the National Gallery of Scotland to help the gallery celebrate its 200th birthday.

Bray admits he was not always a fan of the restored painting.

"It has grown on me, I have to admit. When I first saw her I thought her expression was pretty weedy, but it's grown on me.

"It is a good example of a baroque 17th century Bolognese painting and Dulwich is the place to come for anyone interested in the baroque."

Great Restorations

One of the trickiest restorations of recent decades was the National Gallery's huge altarpiece, Cima's The Incredulity of St Thomas, partly because of the sorry state it has been in for much of the last 200 years. Commissioned in 1497 and completed in 1504, the altarpiece was already in bad condition when it was submerged in the salty water of Venice's Grand Canal in the 1820s. The flood, at the Accademia, caused major damage but did not stop the National Gallery buying it in 1870 for £1,800.

The work needed almost continuous blister laying. In 1947, when the extremely cold winter led to the gallery's heating being turned up, it suffered more flaking than any almost any other picture.

It was not until 1969 that it was taken out of the stores and the dramatic decision was made to transfer the painting to a new panel. It was an enormous risk but successful and the work now looks serenely down on visitors to room 61.

John Martin's The Destruction of Pompeii and Herculaneum was also the victim of flood. This time it was 1928 and the desperately out of fashion Victorian painter's work was in Tate's basement stores on Millbank. The Tate suffered its worst flood when the Thames burst its banks, causing terrible damage to works.

The Martin was torn in two and lost about a fifth of its surface, including the volcano. It was considered "damaged beyond repair".

In 2010, with this year's big Martin show in mind, it was decided to restore the painting's missing section.

Now, if you look very closely, you can see which is Martin's brushwork and which is restorer Sarah Maisey's. She said: "I've tried to tone down a lot of the detail. I wanted the overall impact of Martin's work to have been retained but ultimately wanted people to be able to appreciate what was left of John Martin's work."